[QGIS-Developer] R: GSoC 2021 QGIS On-the-fly Raster Calculator proposal draft review and feedback

Tue Apr 13 07:06:14 PDT 2021

Big interest on my side too (and I'm sure countless more).

I always thought ESA's SNAP had a winning formula with their virtual raster
bands, glad we can make any move in that direction.

Math

On Tue, Apr 13, 2021, 20:57 Matthias Kuhn <matthias at opengis.ch> wrote:

> Hi Francesco,
>
> This is a great initiative, thank you for taking on this.
> I have just recently had a project where this would have been of great
> value. I'm very much looking forward to this work.
>
> Welcome on QGIS board and enjoy your GSoC.
>
> Matthias
>
> On Tue, Apr 13, 2021 at 3:41 PM Francesco Bursi <
> francesco.bursi at hotmail.it> wrote:
>
>> Hi Alister,
>>
>> Thank you for the feedback.
>> Well, I imagine the new feature with some properties of the existing
>> Raster Calculator but not exactly the same, e.g It won't be possible to set
>> layer extent / output CRS, because this would be already pre-defined by the
>> layer on which the renderer is applied, in the basic mockup you should not
>> see these 2 field. The same can be said for choosing other layer. It should
>> work like contours/hillshade renderer, where you can style only the layer
>> you have currently selected but you can choose the band.
>> Besides, I think that the existing Raster Calculator in the processing
>> toolbox (as well as the Gdal Raster Calculator) allows the creation of a
>> temporary file, enable the addition of a layer to the project that you can
>> style, but maybe here I misunderstood what you meant.
>> One of the advantage of the on-the-fly (styling) is to  * avoid the need
>> to create derived raster files and layers.*
>>
>> Let me know if I misunderstood something and thank you for the message.
>>
>> Kind Regards,
>>
>> Francesco Bursi
>>
>> ------------------------------
>> *Da:* QGIS-Developer <qgis-developer-bounces at lists.osgeo.org> per conto
>> di Alister Hood <alister.hood at gmail.com>
>> *Inviato:* martedì 13 aprile 2021 14:10
>> *A:* qgis-developer at lists.osgeo.org <qgis-developer at lists.osgeo.org>
>> *Oggetto:* Re: [QGIS-Developer] GSoC 2021 QGIS On-the-fly Raster
>> Calculator proposal draft review and feedback
>>
>>
>> Hi,
>> This functionality would be great, but as a user, I can't help thinking
>> the proposal is to implement it in the wrong way.
>>
>> If implemented as a renderer, as described, you could conceivably use an
>> expression that uses other layers but not the layer you are supposedly
>> rendering.  What is displayed would not correspond in any way to the actual
>> layer... Bizarre.
>>
>> Would it not be possible to instead implement a "virtual raster"
>> *provider*?  Add a checkbox in the raster calculator labelled "create as
>> virtual raster".  Create a new layer that can be styled using the existing
>> renderers and behaves in every way like a non-virtual layer - e.g. the
>> right values would be shown using the identify tool and the "value tool"
>> plugin, and you could use the layer as an input for other processing tools.
>>
>> Regards, and best wishes with the proposal,
>> Alister
>>
>> Date: Mon, 12 Apr 2021 12:20:53 +0000
>> From: Francesco Bursi <francesco.bursi at hotmail.it>
>> To: qgis-developer <qgis-developer at lists.osgeo.org>
>> Subject: [QGIS-Developer] GSoC 2021 QGIS On-the-fly Raster Calculator
>>         proposal draft review and feedback
>> Message-ID:
>>         <
>> VI1P190MB038187BB910511B3B6B8B44280709 at VI1P190MB0381.EURP190.PROD.OUTLOOK.COM
>> >
>>
>> Content-Type: text/plain; charset="windows-1252"
>>
>> Hello QGIS Dev,
>>
>>
>> I?m Francesco Bursi, an M.Sc. civil engineer from Italy currently
>> enrolled in a Master of Advanced Studies (Level 8 EQF) in giscience and
>> geoinformatics at the University of Padua.
>>
>> I?m really interested in the QGIS (possible) new rendering feature that
>> involves raster calculator capabilities, I've already discussed the project
>> with mentors Martin Tobias and Peter Petrik and possible co-mentor Roberto
>> Marzocchi,  they gave me a lot of feedback and advice for the project.
>> I would like to share my proposal with you before the final submission.
>> Don't hesitate to give me feedback and ask me question/clarification or
>> point me out what's missing.
>>
>>
>> proposal 2021<
>> https://docs.google.com/document/d/1u8L_L1IJjGCZ3d8Vq8duxHbsHZeyzwqOe3tXa1JcKbs/edit?usp=sharing
>> >
>>
>>
>> I'm open to advice, remarks and criticism in order to improve.
>>
>> I am looking forward to a feedback, thank you for your time.
>>
>>
>> Best regards,
>>
>> Francesco Bursi
>>
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